The primary objective of the proposed research is to provide quantitative anatomical and behavioral data relating to the detailed structure and functional significance of the fovea as it occurs in non-mammalian vertebrates. This highly specialized retinal area appears to differ both in morphology and perhaps also in function from the fovea found only in primates, among mammals. The proposed set of studies will contribute substantially to the development of a more rigorous and quantitative body of knowledge concerning the nature of focal vision in non-primates; whereas previously, he literature has contained reports which are primarily anecdotal and speculative in character. Research techniques to be utilized in the present series of studies are: (1) quantitative light-microscopy analysis of receptor and ganglion cell distributions in the foveal retina of species belonging to four major classes of vertebrates, (2) ophthalmic laser-produced photocoagulator foveal lesions in combination with degenerating bouton silver-stain techniques to determine the central nervous system projections of the fovea; (3) optokinetic nystagmography before and after foveal lesions to assess the role of the fovea in oculomotor, field-holding reflexes; and (4) operant, animal psychophysical procedures to obtain measures of visual-acuity (minimum-separable) before and after foveal lesions in the Northern Blue Jay, a species with a highly developed convexiclivate fovea which appears distinctly different morphologically from the primate fovea.